Precision radio dial



Jan. 10 1939. v. CLARKE 2,143,647

PRECISION RADIO DIAL Filed July 9, 1937 INVENTOR g ib/01" lar/fe ATTORNEYS Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE Pan American Airways Corporation,

Jersey City, N. 3., a corporation of Delaware Application July 9, 1337, Serial No. 152,750

7 Claims.

This invention relates to radio dials and more particularly to tuning dials for radio receivers and transmitters that require fine, accurate tuning to the desired frequencies, and returning exactly to any originally tuned frequency.

The principal object of the invention is to produce a dial construction which allows micrometric adjustment of the associated tuning mechanism to a plurality of different frequencies.

Another object of the invention is to produce a dial construction which allows the tuning mechanism to be changed to different predetermined frequencies, quickly and with extreme accuracy.

One form of device embodying the invention consists of a dial plate associated with the controlling shaft of the tuning device and having a plurality of adjustable elements, which may be moved on the dial plate to approximate positions corresponding to the desired frequencies. These elements are provided with screws which may Ice-screwed into and out of the blocks and which have an inclination relative to the shaft at a comparatively acute angle, so that inward and outward movement of the screws varies the dis- 5 tance of their ends laterally from the center line of the adjustable elements. The tuning device may be adjusted by a pivoted lever or arm carried on the tuning shaft, which is provided with means for engaging the screws to regulate the angular displacement of the shaft.

The dials embodying the invention have many advantages, such as accurate micrometric adjustment of the tuning device to the desired frequencies and rapid shifting of the tuning mechanism from one frequency to another without loss of the originally fine adjustment or requiring readjustment or recalibration to the desired frequencies.

Other advantages will be apparent from the description of a typical form of dial embodying the invention, such as that disclosed in the accompanying drawing, in which:

Figure l is a top plan view of one form of my improved radio dial;

1-, Figure 2 is a side View of the dial. with the dial plate shown in section, and

Figure 3 is a side view of the dial partly broken away.

In the form of the invention illustrated, the

radio dial consists of a dial plate It shown as being in the form of a circular disk having a central aperture l2 therein for receiving a sleeve I 4 on the frame of a variable condenser it or other tuning element. The sleeve M is threaded 55 and provided with a nut I6 for locking the dial plate Hi to the condenser framework. While the dial plate i0 is illustrated as circular, it make take any other desired shape, such as for example, rectangular, square, or other non-circular shape, as desired. A condenser shaft I8 carrying the rotatable condenser plates passes through the sleeve l4 and receives on its free end a split block 25, which may be adjustably clamped to the shaft 18 by means of a set-screw 22.

The block 20 is provided with an arm 24, pivotally connected thereto for movement toward and from the dial plate Ill. The arm 24 serves as a lever for rotating the condenser shaft to vary the capacity of the condenser. The outer end of the arm or lever 24 is provided with resilient clip member 26, which forms with the arm 24 a yoke for receiving the heads of selector screws 28.

The selector screws 28 are threaded into blocks 30, which are adjustable in an annular groove 32 in the dial plate It]. The selector screws preferably lie in a plane parallel to the plane of the groove 32 but are inclined at an acute angle to the tuning shaft Hi. This construction allows very fine adjustment of the screws laterally with respect to the median line of the blocks 36, in that by screwing the selector screws inwardly their heads are moved clockwise, as viewed in Figure 1, and counterclockwise upon unscrewing of the selector screws 28.

As illustrated in Figures 2 and 3, the blocks 36 are provided with downwardly projecting lugs 34 which are receivedin the annular groove 32 to prevent rotation of the blocks relative to the dial plate. The groove 32 is undercut to receive nuts 33 of greater width than the upper portion of the groove 32 and which cooperate with the blocks through setscrews 38 to clamp the blocks in any desired position in the grooves. Enlarged holes or apertures 48 may be formed in the dial plate l0 and opening into the grooves 32 to facilitate insertion of nuts 36 into the undercut portion of the groove.

The selector screws 28 are provided with an annular collar or stop shoulder 42, which is adapted to engage the arm 24 to limit its movement toward the dial plate l0. Also the screw may be provided with a cylindrical head 44 of proper width to fit between the arm 24 and the clip 25, thereby retaining the arm against the cylindrical head 44 and the shoulder 42 at any predetermined setting of the screw 28.

In operation, the blocks 30 may be adjusted closely to the desired position for obtaining the required capacity to tune the device to a predeiii) - tuning device.

termined frequency. The arm 24 is then moved to engage the head 44 of the screw between the clip 26 and the arm. Thereafter the selector screws 28 may be turned in or out, as required, to give a very fine adjustment for the frequency of that position of the tuning mechanism. The remaining blocks and selector screws may be adjusted in a like manner to positions corresponding to the other frequencies desired. Thereafter when it is desired to tune accurately and rapidly to any of the desired frequencies, it is only necessary to lift the tuning arm 24 and swing it into engagement with the desired'selector screw so that the head 44 of the screw will be received between the clip 26 and the arm 24, with the arm in engagement with the shoulder 42.

Where extreme accuracy is required over a wide temperature range, an error will be introduced with the use of the more common metals or alloys due to thermal expansion, or contraction, of various parts of the precision dial and especially the selector screw. This error can be minimized by the use of some material having a low coefficient of temperature expansion such as Invar. Another detail of construction to eliminate the effect of expansion in the pivot arm is to design the parts so that the plane of the surface of the lever, which comes in contact with the head of the selector screw, goes through the center line of the shaft to be controlled.

It will bev understood from the above description that I have produced a simple and effective device embodying few moving parts, which produces extreme accuracy in adjustment of the It will also be understood that the dial may be used with any desired type of tuning device without departing fromthe invention. Therefore the above described embodiment should be considered as illustrative only and not as limiting the scope of the following claims.

I claim:

1. In a radio dial, the combination of a dial plate, a tuning shaft, a pivoted arm on said tuning shaft, a plurality of blocks on the dial plate adjustabIe concentrically around the shaft, and means adjustable inwardly and outwardly of said blocks and inclined to the shaft selectively engageable with said arm to control the angular displacement of said shaft.

2. In a radio dial, the combination of a dial plate, an annular groove in said plate, a plurality of blocks adjustably mounted in said groove, selector screws adjustable in said blocks and inclined to the dial plate, a tuning shaft concentric with said annular groove, an arm pivotally mounted on said shaft for movement toward and from said dial plate, and means on said arm for engaging any of said screws to accurately control the angular displacement of the shaft.

3. In a radio dial, the combination of a tuning shaft, a dial plate, an annular groove in said plate and concentric with the shaft, a plurality of blocks adjustably mounted in said groove, selector screws threadedly engaging the blocks and inclined to the shaft, stop shoulders on said screws, and a lever mounted on said shaft having means for gripping a screw and engaging its shoulder to control the angular position of the shaft.

4. In a radio dial, the combination of a tuning shaft, a dial plate, an annular undercut groove in said plate concentric with said shaft, a plurality of blocks having portions slidable in the groove, means in the groove cooperating with the blocks to lock'the latter in predetermined positions, screws threaded into the blocks and inclined to the axis of the shaft, shoulders on said screws, an arm connected to said shaft for rotating the shaft and for pivotal movement toward and from the dial plate, and means on said arm for receiving a portion of a screw and engaging its shoulder to accurately control the angular displacement of the shaft.

5. In a radio dial, the combination of a tuning shaft, a dial plate, a plurality of blocks on said plate adjustable concentrically of said shaft, a selector screw threaded into each block at an acute angle to the axis of said shaft, a stop shoulder on each screw, an arm mounted on said shaft for pivotal movement toward and from said dial plate, a laterally projecting clip on said arm cooperating with the arm to receive a portion of the screw and retain the arm in engagement with the shoulder of the screw.

6. In a radio dial, the combination of a plate, a tuning shaft, 2. pivoted member operatively connected to the tuning shaft and having a clip element adjacent its free end, and means on the plate adjustable inwardly and outwardly and inclined with respect to the plate and selectively receivable between the said clip element and the pivoted member for determining the angular displacement of the said shaft.

7. In a radio dial, the combination of a plate, a tuning shaft, a member operatively connected to the said tuning shaft and movable toward and away from said plate, a plurality of locating means on the plate adjustable concentrically around the shaft, and means adjustable inwardly and outwardly of said locating means and inclined to the shaft and selectively engageable with the said pivoted member for determining the angular displacement of the said shaft.

VICTOR CLARKE. 

